The Plane of Water
Overall, Nautileus is a massive oceanic realm. Very few island clusters are sparingly present so that land-based creatures can have a safer chance visiting.
These few and sporadic isles purely exist for creatures of the land to thrive or visit the plane as an entryway. The countless inhabitants down below could care far less about who runs it so long as their ambitions don’t meddle beneath the waves.
At the bottom of the endless sea, but not deep enough to deny the sunlight of its presence, is what travelers come for most. The Barnalithe Fortress is the heart of the Caperrith Kingdom which Listrum rules over.
There is a region, like a line, where deep and dark creatures of the waters dwell. The area is untouched by any sunlight and that is where vile Piscatorn monsters dwell.